The velocity of the ball?

Two soccer players kick a ball back and forth toward each other. They start off 50 meters apart, and walk toward each other with equal speeds. They kick the ball continuously until they meet in the middle one minute later. What is the magnitude of the ball’s average horizontal velocity in meters per second?

2. Relevant equations

I have no clue of how to solve this, can anyone give some guide, please? :(

In physics (English), "velocity" is a vector. "Speed" is the word for magnitude of a velocity vector. I don't think Spanish has the same kind of word mapping (la rapidez for speed?). Perhaps you could use "vector de velocidad" = velocity and "velocidad" = speed, I suppose.

The definition of "average vector of velocity" is very specific. It involves displacement. Anything in your textbook?